The invention is directed to a hearing aid of the type having a microphone unit with at least two microphones for generating at least two microphone signals, and a signal processing unit supplied with the microphone signals which generates an output signal therefrom, wherein signal components of the microphone signals are amplified and/or attenuated in a directionally dependent manner, and a reproduction unit connected to the signal processing unit from which the output signal is emitted. The invention is provided for use in all types of hearing aids, however, the invention is especially suited for highly developed hearing aids that, for example, have digital signaling processing components.
European Application 802699 discloses a method for electronically increasing of the spacing between two acousto-electrical transducers as well as the application of this method in a hearing aid. The phase shift between the signals registered by the acousto-electrical transducers is thereby first identified. Subsequently, at least one of the signals is supplied to a phase shifter.
A hearing aid of the above general type is disclosed in German Patentschrift 43 27 901. Here, a signal processing unit serves the purpose of achieving a predetermined directional characteristic on the basis of a suitable mixing of signals of a plurality of microphones. The properties of this directional effect, however, are permanently prescribed. Signal components from lateral signal sources are always attenuated and signal parts from signal sources arranged in front of or behind the hearing aid user are amplified.
Given this hearing aid, therefore, little flexibility is established in the case of changing auditory situations. Noises from signal sources behind the hearing aid user are not attenuated. The attenuation mechanism, which also necessarily deteriorates the wanted sound reproduction, is constantly active. The reproduction quality of the hearing aid is therefore not optimum when no unwanted noise attenuation is required in an auditory situation.
An object of the invention, accordingly, is to avoid the aforementioned problems and offer a hearing aid as well as a method for processing microphone signals in a hearing aid having high transmission quality and noise suppression in numerous auditory situations.
The above object is achieved in a hearing aid, and in a method for processing signals in a hearing aid, of the type of initially described, wherein a signal analysis unit is employed for undertaking a directional analysis of the microphone signals, and wherein the signal processing unit of the microphone signals, and wherein the signal processing unit modifies at least one property of the directionally dependent amplification and/or attenuation dependent on the directional analysis made by the signal analysis unit.
The invention proceeds on the basis of the idea of varying the properties of an existing directionally dependent amplification/attenuation according to the result of an additional signal analysis. Thus, an especially good adaptation of the inventive hearing aid to different auditory situations can be realized. For example, the direction of a noise source can be taken into consideration in the directionally dependent amplification/attenuation in order to offer good noise elimination. When no noteworthy unwanted sound is present, in contrast, the noise attenuation can be switched off in order to minimize distortions.
The modification of a property of the directionally dependent amplification/attenuation assumes a directional dependency of the amplification/attenuation that exists without this modification.
In preferred embodiments of the invention, the intensities of signal parts of the microphone signals in a number of predetermined direction classes (angular ranges) are defined in the direction analysis. As a result, the approximate direction of the principal component of a noise source can be identified. Alternatively, the direction of one or more signal sources can be determined more precisely.
An adaptive LMS filter can be employed for the signal analysis, signal distortions, in particular, being estimated therewith by whole multiples of a sampling cycle. The coefficients of the LMS filter determined by the adaption event can influence the result of the direction analysis or (completely) define it or even represent this result themselves.
Dependent on the result of the signal analysis, different signal processing steps can be implemented in preferred embodiments. For example, the directional characteristic of a directional microphone (a virtual directional microphone formed by superimposition of the microphone signals) can be suitably modified. Such a modification can, in particular, be an alignment of the directional microphone pole. Alternatively or additionally, a suitable noise elimination method can be selected.
Weighting signals, that determine the weighting factors with which the results of different filter, noise elimination and/or directional methods enter into the output signal, are preferably generated in the evaluation of the signal analysis.
The microphones for generating the microphone signals in preferred embodiments are arranged at a relatively slight distance of at most 5 cm or at most 2.5 cm or approximately 1.6 cm from one another, whereby the connecting line between the microphones can extend at an angle of at most 45xc2x0 or at most 30xc2x0 relative to the line of sight of the hearing aid user or can lie approximately in this line of sight. In particular, a common housing can be provided for both microphones.